Evaluation of Antibiofilm Activity of Nigella sativa and Olive Oils’ Nanoemulsions against Bacillus cereus from Dairy Processing Plants

Kariesh cheese, ice cream, and pasteurized milk are among the popular dairy products with high nutritive values. These products are commonly consumed in Egypt at all ages. However, the surrounding surfaces and equipment might lead to contamination of such dairies with foodborne pathogens such as Bacillus cereus. Microbial biofilm production is a developed mechanism that enhances survival and resistance to harsh environment along with spores. This study aimed to investigate the prevalence of B. cereus in dairy products including kariesh cheese, ice cream as well as pasteurized milk, dairy plant surfaces, and equipment. Besides, the ability of the identified B. cereus isolates to produce biofilm were further examined. In a prevention trial, Nigella sativa and olive oils’ nanoemulsions were used at a concentration of 1%, and 2% to reduce B. cereus biofilm formation. The obtained results revealed isolation of B. cereus from the examined kariesh cheese, ice cream, pasteurized milk, dairy plant surfaces, and equipment at 44%, 16%, 8%, 72%, and 68%, respectively, with average counts of 3.69 ± 0.23, 2.58 ± 0.19, 2.15 ± 0.21, 5.36 ± 0.39, and 4.46 ± 0.59 log 10 cfu/g, respectively. Molecular confirmation of the recovered B. cereus isolates revealed that all isolates harbored B. cereus -specific 16S rRNA, and Cal Y, biofilm-matrix protein. All B. cereus isolates had the ability to produce biofilm. Nigella sativa, and olive oils’ nanoemulsions reduced B. cereus-produced biofilm in a concentration-dependent manner.